I have a 2019 model Cube Attain which I purchased in September 2019 and has done over 4000 miles since then.
Good points:
1. Value. I couldn't see many other bikes with hydro discs and full 105 at this price point.
2. Reliability of frame. I have hammered this bike along country lanes, winter and summer and gravel by ways. The frame is still unmarked. Great paint job. No sign of stress anywhere.
3. Comfort. I use this bike for Audax and long rides. It is pretty comfortable. Quite upright stack. Seems to handle endurance riding well. I like the saddle - as good as my Fabric Scoop. The bars and stem, whilst not branded, seem up to the job. The wide tyres also help.
4. Tyre flexibility. Cube suggest 28mm max ( and supply tyres this size) but I am currently running 32 mm Panaracer Gravel Kings - but without full mudguards. 30mm may fit with guards if you can find any that fit apart from clip on.
5. Weight. Comes in under 10kg (just) and is fast enough for this kind of bike. It won't win races but it does keep going.
6. Handling. Predictable, safe but not boring.
Considerations (everyone will have different experiences here)
1. Wheels. I got through bearings on both wheels quite fast. Then I broke a rim. I have replaced the wheels with Mavic All Roads which have been far tougher.
2. Mudguard mounts. There are apparently some Cube guards that will fit into hidden slots on the forks and stays but I can't see how. I haven't bought them. There is nothing on the bridge or top of the forks that I can detect. This means clip on guards.
3. Bottom bracket. I wore it out in 1500 miles. The LBS replaced with a better version and fixed it in more securely and since then no issues.
I like the bike. We have become good friends over our miles together. I would recommend it apart from the problem with fixing guards.