Not truly that recommended.

Unless you are into stronger haloation around finer, sharp-ish details. It can work sometimes. Giving off that more romantic look, you know. But i you want crisp sharp details - an extension tube with NATIVE Fujifilm GF lenses, which almost all use floating lens elements (FLE) - will degrade the optical performance by a lot. Including their so called 120mm (1:2) Macro lens, suffers from it.

You would have to stop down the aperture by a lot (3-4 stops) in order to counteract, the drop in sharpness - at least partially.

I just tested a 11mm extension tube it with the Fujifilm GF 110/2 lens - but boy - it was not simply not it. I did not even save the images. The degraded optical quality / sharpness just felt... hurrk. I believe / from what I understand, almost all Fujifilm GF lenses uses FLE.

Sigma 70mm ART Macro also has FLE

Also the fantastic Sigma ART 70mm ƒ2.8 Macro lens uses FLE. When you use it without a tube, it performs admirably well on Fuji GFX cameras. Being seriously sharp ! In fact, it is razor sharp, making it well suited for Macro (as well at infinity). Only when you get really really close, you get some soft vignetting.

I find it to be a highly recommended lens for anything you desire to picture close, with a Fujifilm GFX camera.

Tubes with NON-FLE lenses

The extension tubes are more useful with lenses that are not exhibiting FLE e.g. do not use floating lens elements . There you actually get a lot better performance (or a much lesser drop in optical quality). Now I personally am not a true believer in extension tubes, especially not the longer ones. I usually only use the shortest ones, in order to get a notch closer if needed.