So I tried to broadcast a signed transaction from an old Electrum version (like 1.7x). I check it on coinb.in and it's valid. But when I try to broadcast it, I get errors like 'scriptsig-not-pushonly'. It's frustrating because I can't seem to get it out there.
Sounds like the TX isn't conforming to the network rules. If nodes are rejecting it, your scriptSig might have some weird stuff going on, not just push operations. Best not to tweak anything when exporting the raw TX. Maybe try updating Electrum and recreating the TX?
Yeah, seems like you’re stuck with a really old version since you’re working offline. Not a great idea. I’d suggest using a newer version of Electrum instead. It’ll save you a lot of headaches.
I checked out that StackExchange link you mentioned, and it looks like your Electrum version creates non-standard transactions. They might work if mined directly but most nodes and miners will probably reject it. Definitely update Electrum and recreate that transaction.
If you've been around since 2011, I bet you've got some crypto you wanna protect. It might take some time, but it’s totally worth it. Once you get the hang of it, 30-60 minutes isn't too bad for peace of mind.
I think you’ve nailed the issue, just like you said. But the link I shared was relevant because it showed the same broadcasting error, so it seemed like the right direction.