Well, the storage and bandwidth for the images is not free. I encourage you to use external image hosting services, like catbox.moe. You should know that these are run by individuals like you and me, with no ads, no selling your personal data, etc.
Then you can embed them using this markdown syntax: 
In most Lemmy apps, there is an interactive UI for your convenience.
You also might consider self hosting your own private instance, like me and a few hundred others. Then you have full control over your instance and with which instances you federate with.
https://forum.affinity.serif.com/index.php?/topic/98932-faq-affinity-on-linux/
They didn’t say they never will. They don’t have plans for it, but they won’t rule it out. (Unless the FAQ is outdated and they said they never will somewhere else)
I guess they could use Flatpaks here if they don’t want to deal with packaging it for every distro.