Sorry to jump in late on this as I've been rather busy for the past few days trying to do various family member tax filings. Both the outdated Moodle that you can install using IONOS app install, and a regular Moodle install can be done, and upgraded
to higher versions of Moodle via git, but it requires some "extra" steps to get it to work.
I have one Moodle site, http://m3x.drachels.com/, that currently is running Moodle 3.9.6+, that started out as Moodle 3.4. A few months after the initial install, I tried in vain to upgrade it with a side loaded git, that always failed. That is, it always
failed until I found this forum entry: https://moodle.org/mod/forum/discuss.php?d=408652#p1649476. Once I completed those four git config changes, git pull, has worked like a charm for the weekly upgrades.
Last week on a "free" day, I decided to see if I could get a Moodle 3.10 install to work the way I did it years ago when Moodle code was much smaller, and a git stall would work. Sin Moodle 3.11 is coming out soon, I wanted to make sure I could at least
upgrade to 3.10. I pre-made a database, user, and password and also premade a moodledata folder for the new 3.10 with a htaccess file. I then logged into a terminal window, and got Moodle 3.10 code via instructions here: https://docs.moodle.org/310/en/Git_for_Administrators,
with one small change like this:
git clone git://git.moodle.org/moodle.git mynewmoodle
For the install to work you do have to apply the four git config's mentioned above. You also need to have a htaccess file in your moodledata folder:
deny from all
AddType x-mapp-php7 .php
I did make my on new config.php and put all the required info in it using my already working one as a guide.
Currently, I do not have https implemented, but plan to when I have some more free time.
I hope you can get yours to work. Gotta go finish my own taxes now.