Installing Magisk fails on latest 20.0 build for `lancelot`

Reported in XDA Forums: https://xdaforums.com/t/lineageos-for-microg.3700997/post-90535864

The project does not provide support for Magisk or similar add-ons: if they work, that is fortunate, but it is not one of our project objectives. So the project will not be spending any time investigating this issue (which is in any case - in our opinion - likely to be caused by, and therefore only fixable by - changes in upstream code).

But this defect is raised in case anyone else is in a position and is motivated to investigate what may be causing the problem, and how it might be either fixed or worked around

Quote from the XDA Forum Post

I am here to report a major issue. In lineage-20.0-20260325-microG-lancelot.zip(for Redmi 9), Magisk has become incompatible. I tried to install all the methods from patching boot.img(the app crashes) and direct install never worked for this rom in 1st place. I have tried with kitsune magisk(didnt work), Magisk v29(didnt work) and Magisk 30.7(which upon installing through recovery caused the phone to get stuck on endless boot. Not bootloop, but the animation would never end). I had to revert back to last stable update(lineage-20.0-20260110-microG-lancelot.zip) and everything worked fine there(yes, I lost most of my data and had to factory reset-which is partially my fault for not making frequent backup). And I did retest 3 times(since I had nothing to loose) on fresh installs of new update but to no avail. One time, even external app manager and package manager was failing to install the magisk app.