Safe to share boot partition? On XDA, at times I see users requesting for boot partitions of a particular version of stock ROM and some people helping out by uploading and linking them.
I am not sure if it is a good practice, mainly because
a)  it may contain sensitive information
b) it may create problems for the recipient, if they use it as John Wu creator of Magisk mentioned in the context of patching boot images
I searched around for answers, but no luck. To localize the problem consider that the question relates to devices with A/B Partitions, while a broader answer is welcome
the tweet doesn't explain the reason but it is unrelated to security. it is not 'safe' to patch a foreign boot.img regarding the functionality of Magisk because of the following reason:
Magisk Manager assumes

cpu architecture
encryption type
encryption state
dm-verity

read from host device is equal target device, it does the patches according to host specifications (where Magisk Manager is currently running, regardless of the origin of boot.img
while this is bad practise, i want to contradict because it will cause issues only in rare corner cases and is (most likely) 'safe' to patch a foreign boot.img