With my prior car, the return pressure was generated by the action of the springs on the clutch assembly inside the transmission. (the springs that hold the clutch disc to the flywheel) So those springs pressed on the throw-out bearing, which pushed on the clutch fork, which pushed on the slave cylinder, which pushed on the master cylinder, which pushed on the
clutch pedal.
Failures were rare, (particularly without regular abuse,) but they were typically in the hydraulic system. About pulled my hair out bleeding the system. Started out filling brake fluid reservoir to tip-top full, all the way up to the lid. I watched the reservoir levels, adding fluid as it bled, never allowing it to get low or really much below the full line on the reservoir for that matter. Longer story short, the reservoir is shared... brake master, clutch master. It's compartmentalized with a spillway. There was a tiny back corner of its brake fluid reservoir, that was dedicated to the
clutch master cylinder. I couldn't see that and was only reading brake fluid level. So the reason I had such a
time bleeding, the clutch master portion in the back corner, was bone dry, but the portion I could see was still almost to the full line.