Correct, the only way to learn about Nextcloud and the hundreds of apps available is to invest your time. It is not easy, but it is fruitful.
Correct, nextcloud.com is for marketing to enterprise businesses and clients.
Documentation is literally handled through Github issue and pull request tracking. You can also try searching the forum. Example: Search results for 'nextcloud tags photos' - Nextcloud community
Or, use the internet with keywords: github photos nextcloud at DuckDuckGo
- This will help you find the Photos github repository
- This is where you will learn the most about tagging support within the photos app.
- issues for discussions, bug reports, road map items, and feature requests.
- pull requests for functionality in actual development.
- You can also search the appstore at https://apps.nextcloud.com/
Or, search for the relevant Github repo keywords with nextcloud photos github at DuckDuckGo
You’ll also find more universal conversations about tagging support system wide on this forum or at the primary nextcloud server github repo using keyword searches like https://duckduckgo.com/?q=github+nextcloud+server+tagging+system+wide&t=ffab&ia=web
You can subscribe through a Github account to follow along with these things as the years go on. It is a gradual process overall, with some items ignored and others seeing furious development. This is why Nextcloud is the top open source project for file sharing. Understandable if this is a lot to process, but it is also the nature of open development at a furious pace.
The answer is basically no, the Lightroom specific functionality is not built as feature parity within Nextcloud. In fact, none of the apps offer feature parity with Google Drive or anything else. But, you can check the photo and server repos linked above to confirm for yourself.