I just installed InvoicePlane on top a LAMP PHP 7.4 and it work like a charm.
I used InvoicePlane for few years, and moved to InvoiceNinja with nostalgia because the main developer of the project was looking for help and decided to move forward. At this time he was suggesting to move to InvoiceNinja and they even develop a script to export/import.
Anyway InvoiceNinja is a great project but I always missed InvoicePlane feeling, which survive through his community.
Long story short to say
I plan to package and maintain InvoicePlane App for Cloudron, anyone are welcome to try it and to comment.