I think I've discovered one neat cloud-free approach to organize the work for a small (research) group and need to share it with someone :)

Setup:
1. PC with internet access (*host*) somewhere in a closet (in our case somewhere in half-forgotten room at the uni, so internet and electricity are almost free)
2. [dokuwiki](https://www.dokuwiki.org/dokuwiki) installed on it. #dokuwiki is a lightweight wiki software running without a database (i.e. pages are plain text files). We use bootstrap3 template and a ton of plugins to make it more or less user-friendly and nice to look at.
3. very cheap vps (1-2 $$) serving as a *gate* for NAT traversal.
4. domain name from freenom for 0$

On *host*: open reverse tunnel with wireguard (see [this guide](https://blog.fuzzymistborn.com/vps-reverse-proxy-tunnel/)) and serve dokuwiki on tunnel's end corresponding to the *host*; on *gate*: some sort of reverse proxy (we use nginx) redirecting the queries to the *host*'s tunnel end IP address.

So, what we got for a couple of bucks:
- group knowledgebase with fine-grained access rules and simple task management (and almost anything can be tweaked by the admin, i.e. me)
- accessible from anywhere with the internet access without any VPN setup.
- to upload media files (pictures and movies) to the wiki we use sftp or syncthing running on the *host* (and bindfs to mount the media folders inside wiki media folder). The disk space is almost unlimited (we have 6tb hard drive plugged in the said pc and more are on the way :)

The obvious caveat is the setup time cost: dokuwiki plugins quality is not always great and they usually require some tweaking to match our needs.