Similarly to the first issue, I solved this one by using a self-compiled version of Sage. It might be useful to mention this detail in the docs. Now fgb_sage works flawlessly with Sage 9.1. I'd still gladly submit a pull request as regards the docs if there's any will.

Could you say how the other Sage was installed?
Via a package manager? apt, conda, pacman, rpm, yum?

Sure, I used this package https://www.archlinux.org/packages/community/x86_64/sagemath/, which I installed using the package manager yay on Arch Linux.

You could maybe reopen this issue and change the title to
"State assumptions on how Sage was installed".
I think a pull request to amend the docs would be nice.
What do you think @mwageringel?

The first two issues in this repo could be renamed:

• Installation fails on apt-installed Sage #1 Install instructions fail on apt-installed Sage
• Installation fails on yay-installed Sage #2 Install instructions fail on yay-installed Sage

So maybe open a third issue for improving the docs,
and refer to those!

Thanks for bringing this up. I was not aware of this – apparently the script sage-apply-patches is only available in Sage the distribution, but in some packaged versions of Sage it is not. I have added a few words about this to the documentation.

The simplest way to fix this might be to copy that file into this repository.

Regarding #1 , the version of Sage (8.1) might just have been too old.

This should be fixed now, finally, at least on Arch. Feel free to reopen if there is still a problem on another distribution.