Sure, but in the end you pay (+ -) the same price for the yongnuo or nissin, and get added optical slave, shorter recycle times, automatic aps-c conversion for the flash zoom, things you don't get with the 550 EX
I agree that your Yn 560 will not play ball.
But beyond that every time you introduce a different brand, you multiply the chance of failure or at least inconsistency in how ETTL II is implemented.
You can still source pristine secondhand Canon 550Exs for equiv. of £130 which would give you a great 'Canon Wireless' network, offering both ETTL & M with HSS for either.
- Canon EOS M58.8%
- Panasonic G85/G803.3%
- Panasonic FZ2500/FZ20001.9%
- Panasonic LX10/LX151.2%
- Panasonic GH5 development3.6%
- Sony a99 II15.9%
- Nikon KeyMission 170 and 801.0%
- Fujifilm GFX 50S development28.3%
- Olympus E-M1 II development18.7%
- Olympus E-PL80.1%
- Olympus 25mm F1.2 Pro1.5%
- Olympus 12-100mm F4 IS Pro1.9%
- Olympus 30mm F3.5 Macro0.1%
- Sigma 85mm F1.4 Art3.6%
- Sigma 12-24mm F4 Art2.6%
- Sigma 500mm F4 DG OS HSM Sport2.4%
- YI M12.2%
- GoPro Hero50.8%
- GoPro Karma drone2.2%