Which external flash is most compatible with Olympus and Panasonic bodies?

So I've got this mix of gear with an older Lumix G9 and just grabbed an OM-1 for some travel stuff since I'm heading to Japan next month. I need a flash that actually talks to both systems properly without me having to buy two different sets of triggers.

I'm torn between:

• Godox TT685O (love the wireless options)
• Used Panasonic DMW-FL360L (way cheaper)

My logic was that the Panasonic might play nicer with the G9 but will it still do TTL on the Olympus? I'm trying to stay under $200 total since I spent way too much on the new body lol. I'm just worried about the Godox build quality or if the Panasonic will feel outdated on the newer OM system...