It isn’t clear how the pricing works in this situation, as the purchase page only gives prices for Mac, Windows and combo, no Linux. For the pro edition combo it is only another 8.35 euro. Whilst I agree it seems silly pay more just to get a decent/functional GUI restore method, its still a nominal amount in the scope of things and cheaper overall than some of the alternatives I looked at. I have asked their support team what to do here.
https://www.syncovery.com/cgi-bin/syncweb.cgi?pg=allprices&id=370522741404184476440384504
This assumes professional is sufficient, in my case it probably is (to get encryption).