So, you can work around these things but you’re going to run into problems if you do:
-If you reset the router, you need to restore the original password else they’ll know
-if they notice you using these devices when you wouldn’t have access, they’ll remove them further from your reach. Possibly permanently.
-If detected, a larger conflict is likely to be escalated. This includes a loss of the benefit of the doubt in the future.
I’d suggest that this is not the battle to fight. They’re likely fighting your apparent obsession with tech. Let them have this battle and continue your fun later.
Try the Stormlight Archive, wheel of time, or mistborn books. Maybe the redwall books if you’re younger. Fun and focus can still be had without a computer!
From a theory perspective alone, ignorant of Lemmy specifics: a database query can be made to list all cached images including a unique identifier for each image. Use this list to find each cached image.
Look at your cached image list and decide how you want to prune it. The most likely pattern for this system is FIFO, so prune the oldest cached data until you drop below the target disk usage.
In practice, you’ll likely use somebody else’s solution. Be sure to read the contents of their solution carefully to ensure it doesn’t move sensitive data to an externally accessible location or exfiltrate data directly.