We are now in a world where the developers never tell you what you need to change, they just imply a change. They may have documented something but good luck finding it. They may have even talked about it publicly, but we all weren’t there to hear or see. Their comments about things are lost in long lists of google results and lost in the wash of time and complexity.
Developers today do this to you… “what is 2+2”? It’s not 3 and it’s not 5. What is it? 10? The answer the developer should give you is “what is 2+2”? … it’s 4 — period. I don’t need to guess. I don’t need to extrapolate. Just give the answer developers.
The point here is that we all have to go through enough, especially with the complexity of today’s software. The computer itself is capable of listing the answer and having the answer displayed in full without making us guess. The developers all do this. When we ask a question don’t say we need to ask the right question, just tell us the answer.
Anyway, in this case, the cause of the error is something they documented over 7 releases ago. The answer is that you have to modify your /etc/php/<version>/mods-available/apcu.ini (or apcu_bu.ini). In version 7.4 (and apparently 7.3) you need the modification in the apcu_bu.ini file and apparently in 8.0 you need it in the apcu.ini file).
The modification for the apcu_bu.ini file is to add two lines:
apc.enable_cli=1
apc.shm_size=512M