After a complete python3 update by Ubuntu 20.04 I can open a maxima-jupyter notebook but I get the message ext.toLowerCase(): No Such Function. Apparently the kernelspec has changed, changing the json required in the kernel/kernelspec.
The problem is that I can find no details on the exact field(s) that are now being required or enforced. Some of them were optional before and they are mandatory.
Is this the discussion for this topic or is there a developer’s mailing list or issue tracker for this?