I still use drops. Kind of quit trusting PH meters\probes years ago, and got tired of spending more time maintaining or worrying about them and 5 more bottles of solutions than anything else.. Seen plenty of super expensive blue lab pens\probes go haywire and ruin peoples grows over the years. Not all user error either.
None of them ever calibrate exactly the same as each other either, not even 2 brand new ones side by side in the same res. Which one is true? Then you have friend bring theirs to check against the others, and its different too, haha..
Takes all but a minute do take a sample with drops, and bottles last years. I always have a few different hydro systems going, sometimes like 5-6 different ones, and no way i'm gonna fork out like $1-150 + the time to build DIY w/ arduino, let alone spend 4-500 for a ready to go blue lab or atlas setup for each individual system, lol. I know it can get advanced, with one unit and 6 probes hooked to wifi...
Always have to pull out the drops anyway in my case, so might as well stick with them for good. I love DIY builds and automation too, but choosing to stick to manual operations when it comes to tending my reservoirs. I prefer to drive manually too..