Baron

https://m.youtube.com/watch?v=PEQAqyC4UNA All the bike manufactures is just waiting to release full suspension gravel bikes to make every one, spend money for a new gravel bike with full suspension.

I have a bike with the Shimano 9 speed Ultegra ST-6510 STI Flight Deck 2/3 Speed Shifter, so you do get a mechanical shifter that can be used for 2 or 3 chain rings.

See now OP say levers is 105 and and drive train Dura Ace, so he can check if his 105 levers is tripple compatible as most pre 2017 105 levers was tripple compatible he can just fit tripple crank set and his problem is solved.

Shimano Dura-Ace Gear/Brake 10!speed Shifter Set Model: ST7801/ST-7803 can be use with double or triple chainset.

Op can check, I do not know if Dura Ace is same, but most Shimano 105 and Ultegra 10-speed left shifter is designed to work with both double and triple chainrings by adjusting the lower and upper limit screws on the front derailleur. These "dual-use" or "dual-purpose" shifters allow for flexibility in the number of chainrings, so you can use the same shifter for a double or triple crankset without needing a separate, dedicated shifter.

Maybe this, still available new. Shimano Tiagra FC-4703 Tiagra triple chainset 10-speed; 50/39/30; triple; 172.5 mm.

Do not know if the are available in SA Schwalbe Hurricane Performance 29x2.25 BIk

Fast all-around tire for the MTB from Schwalbe. With its fine pattern on the top and larger knobs on the sides, the tire ensures a low rolling resistance on straight roads while also ensuring a good grip in turns and on softer/looser surfaces. This tire is the obvious choice for the rider who wants good speed on the roads and at the same time has the opportunity to turn in the forest or on a dirt road.

Fix it. After 9000km still 100%.

Carbon chainstay? Where did your chainstay break/crack?