I’ve done all that’s needed from a phone
Termux has git and mc (mcedit) or whatever vim or emacs or joe
git clone https://gitlab.com/YOURACCOUNT/fdroiddata.git
cd fdroiddata
git remote add upstream https://gitlab.com/fdroid/fdroiddata.git
git checkout master && git fetch upstream && git pull --rebase upstream master && git push origin master
(this is the secret sauce to bring your fork in sync with the main)
put credentials as asked
git checkout -B mybranchname
mcedit metadata/... (this is the tricky part since you kinda need to get it perfect from the first try)
git commit -a -m "describe my fix"
git push origin myedit
you’ll get a link in the output
open browser, paste
login to Gitlab, submit MR
…
Next MR?
git checkout master && git fetch upstream && git pull --rebase upstream master && git push origin master
…you know the drill 