I do not think the 3ed canon portals can be justified under 5ed canon assumptions, but it is very useful to have them collated as a research aid.
I was sort of on the fence about it too, but decided to include them for completeness. The Greater Alps portals are sort of iffy too as they were all Hermes Portals but the cost of maintaining those has changed from 4e->5e. In the annotated maps I've noted that the state of the Greater Alps and Iberian portals is very much a saga decision because of this.
The Verdi and Rellantali portals in Rome are 3e too, but they seem plausible to me. Verdi moreso than Rellantali by virtue of being a Domus Magna and founder covenant.
Colour coding by edition is a good idea, and I probably should have included a legend in hindsight but I made these for my own use and only thought to post them as an afterthought. Case in point:
BTW. I am not sure I understand the difference between dashed and solid lines.
Dashed lines are for portals that aren't functional in 1220, but exist as either deactivated portals like Val Negra<->Harco or which are under construction or planned at the standard start date like Oculus Sept.<->Durenmar which Philippus Niger is pushing hard for according to GotF, but hasn't actually been built by 1220.
You're right there is a defunct one from Durenmar to Rethra, I missed that. The Lübeck portal doesn't exist in 1220 it's just mentioned as something Philippus Niger is pressuring for to happen, hence it being a dashed line.
Thanks for getting me to think about Rethra, I think that it's giving me an idea for "season 2" of my game: a disastrous joint venture by Irencilla/Roznov to repopulate it, after the Occulus jumps to the Lotharingian Tribunal, so that the Rhine has a "sea port" Covenant.
As for the edition shifts, I tend to look at 5th with some economics in mind. I would think often covenants would prefer pay House Mercere a big chunk to make a permanent portal rather than repeating the rituals annually.
I wonder, to what extent would the redcaps use portals? The portals have proved a security risk, and one had better be sure that one can defend both ends. Is it really sustainable in tribunals with such small Hermetic populations as are found in Novgorod and Loch Leglean? Would they risk it in a frontier tribunal like the Levant or in tumultuous tribunal like Hibernia? Is it really a good idea to have one at a Mercere House without an Aegis (e.g. the one at Coventry), or maybe they have Gifted magi who make Aeges to protect portals?
Of course, it is a saga call, and it depends heavily on other assumptions about politics, stability, and antagonists in the setting. Personally, I find that I like the pedestrian redcaps as a theme, with personal contacts and trade across borders. I find it rather boring to see the redcaps as a pan-European mail order service, where goods are procured as easily from the Levant as from Stonehenge. Therefore, it works perfectly fine for me to have the Mercere House in Coventry serve all of the British Isles. It isn't a long journey across to Ireland, and the journey to Scotland is much shorter than the one across Scotland. But of course, that is me tending towards low-powered sagas.
The map is certainly a good starting point for further thinking about it.
Would the Mercere ever make portals for others, even if they pay? After all, they keep it a secret, but when somebody is able to study a portal for a season, they can in principle reinvent it as well.
Would anyone use Hermes' Portals in 5ed rules? It is rather expensive and also difficult to organise.
There are some details about how portals were originally used and how that changed after the schism war in HoH:TL that are crucial imo:
There used to be a lot more portals and they were open to any magus, until that got abused hard during the Schism war.
Mercere the Founder linked Durenmar with the covenants of each founder.
Later his followers built outposts to keep up with the expanding order and linked them to Harco. Novgorod, the British Isles, and the Holy Land are mentioned by name.
After the Schism war a lot of covenants had their portals removed or new ones enchanted outside the covenant at a more defensible position.
Since the schism war it is standard practice to enchant portals with special passwords or other security mechanisms. Many have triggers that mean only a member of house Mercere can activate the portal.
Most portals have a permanent redcap custodian who activates the portal for travellers after checking their identity and business. They also prevent anyone from studying the portals and destroy them if danger arises.
Personally for my sagas I take the general view that there are still two major networks, but private portals are very hard to commission - needing a very, very established covenant or exceptionally good relations with house Mercere (good enough that they are willing to station a redcap there permanently).
Almost every tribunal has a portal to the Harco network somewhere, but they have redcap guardians and can't be activated by non-Mercere regardless. Any attempt to force access would see the portal destroyed, either by the guardian or remotely from Harco by spell.
The event that got me looking into this involved a deal to get a Mercere portal built, and it required the calling in of old favours by a neo-mercurian magus with strong social ties to house Mercere, a very senior redcap vouching for the covenant, and the trading of some very valuable original research to the Mercere (involving longevity magic which does not cause infertility). So that's the sort of level we set for "why would the Mercere build a portal for someone else?" in our saga. For our saga that portal will be the only private one in the British Isles (the covenant is in Stonehenge), period.