Why did you lock it to Epic speed? Could you make it customisable, or release one with the scenario but on quick or standard speed?

If the map (and the scenario check box) doesn't show, you have to copy the map file manually. If you look at the last slide in the scroll above, I explain how it's done. Much fun with the map!

The map does not show up in the additional maps. I have turned on the mod. Is the mod not compadible with map?

Map Only version posted to Workshop, as promised: https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1281283483

The scenario editor forces you to set a Game Speed that then can't be changed. Epic is just an expression of my personal preference: I always play on Epic and Hard. I'll post a Map Only version for this map mod, too. On those you set all settings. Already posted the one for the Continents++ map, need to find some time to prep it for this one. Before end of week for sure.

I have to ask, why the forced Epic game pace?

Perfidious Albion describes the UA of England when you activate the Vox Populi set of mods (link above): it get's a spy on start, which allows for a tech-centered strategy. You can focus on doing cutting edge research (for me when England it's usually the maritime techs), because your spy will eventually steal the lower level technologies you neglected from other Civs you send him/her to.
I can't really speak highly enough of that Vox Populi project: if you install and run all its mods, it's like you purchased another expansion, like G&K or BNW. Only - of course - you get it free. An incredible, incredible value. I've played with it constantly for the last year, and can report to never have run into a bug.

Perfidious albion?

Word of warning: this map is truly huge. You will need a computer with at least the recommended specs for Civ V to play this map into the modern age.

Aren't 21 Civilizations a bit much? Actually, no. On the contrary: this map is so huge, having fewer than 21 Civs would mean a very repetitive gaming experience. After 10 settlements, the ever same Monument-Shrine-Next Building routine gets tiring. With these 21 Civs, anyone has - at most - 10 uncontested settlement opportunities. Some Civs have even less because they start in desirable locales - so be prepared to adjust your strategy accordingly.