Adding to my comment since it was downvoted:

There are two parts of "sending encrypted files": the encryption and the sending. An offline tool (e.g. PGP or age) seems only necessary when you want to decouple the two. After all, you can't do the sending with an offline tool (except insofar as you can queue up a message while offline, such as with traditional mail clients).

The question thereby becomes "Why decouple the sending from encryption?"

As far as I can see, the main (only?) reason is if the communication channel used for sending doesn't align with your threat model. For instance, maybe there are multiple parties at the other end of the channel, but you only trust one of them. Then you'd need to do something like encrypt the message with that person's key.

But in the use-case you mentioned (not wanting to publicly post a log file), I don't see why that reason would hold; surely the people who would send you logs can trust trust Signal every bit as easily as PGP. Share your Signal username over your existing channel (the mailing list), thereby allowing these people to effectively "upgrade" their channel with you.