This, with a good backup plan, looks like the sensible way to go based on what you want to do. I see people mentioning piwigo, that is a great choice if you want some advance photo hosting features, have multiple users, manage permissions (or not), but the content is not stored in a way that makes it easy to retrieve.

With nextcloud (and the autoupload on your phone), all your photos are accessible from any browser and you can still easily share content with generated links with preconfigured expiration, … Sure nextcloud does a lot more and may be a bit overkill for what you need but it should be easy to get running and the other features could be put to use without any doubt.

The other simple solution would be a simple photo gallery, with a sftp client on your phone, I used minigal nano in the past but it seems to be unmaintained. I’m sure you could find an alternative. From a quick search lychee and librephotos seem like a couple of good examples and photoprism which has been mentioned here.