Well, the writing was on the wall for some time but this confirms it - it seems Feral Interactive aren't likely to do more Linux ports with the official port of A Total War Saga: TROY for Linux cancelled.
It was announced today that TROY would be finally seeing a Steam release on September 2. Feral did their usual thing on Twitter of quote-tweeting, mentioning it would be on macOS soon after the Windows release. A mention of Linux was totally absent.
Feral replied to a user on Twitter to say:
The Linux port was put on hold while TROY was exclusive to Epic, and we are not resuming development for the Steam release. We will continue to assess the feasibility of porting games to Linux, but there is generally less demand for native titles since Valve’s launch of Proton.
Considering there's a chance that Steam Play Proton might be able to play it from day-1, it's not overly surprising to hear this from Feral considering the cost of porting bigger games with it being far easier for indies. Worth also noting, that TROY was free on Epic Games Store when it first launched, so it would have already eaten into plenty of possible sales.
Part of the problem though, is how most Feral ports lack cross-platform multiplayer with Windows and that type of thing simply won't fly on the upcoming Steam Deck. Add into that issues with saves between the Windows version and Feral ports, that could cause more confusion if they don't sync up. Not only that but since the Steam Deck is basically a PC in handheld form, seeing bigger titles launch for it officially months or years later also wouldn't be a good look.