I've use 2 "dashcams" on every ride.
I've had a Contour Roam2 mounted on my helmet for the last few years. It's adequate, and easy to operate as it has a slider that turns it on so I just have to remember to reach up and turn it on before every ride. I have to take it off to charge it after every ride but that's not a big deal for me. However, there are 2 things I have found to be issues.
The first is battery life. When I first got it, it would record for almost 4 hours, but after several years of daily use, it would last under 2 hours. I was able to increase that to around 2 hours 20 minutes by tweaking the settings to record at a lower setting without appearing to affect recording quality. It will not operate if there is a charging cable plugged in as you have to flip up a cover to access the charging port, and the battery is NOT removable or replaceable..
The second issue is that it does not over-write files. If I forget to delete the previous files, it will just stop when the sd card is full. I have a fairly small sd card so I end up having to delete files after around 4 hours of operation. You can do this either via a button on the back of the unit, or by connecting it to a computer and deleting the files via file manager. Note that battery life is the critical factor as just getting a bigger sd card won't do much for you except reduce the frequency at which you need to delete the files.
My 2nd dashcam is a free phone app called Dailyroads Voyager. I installed this on an old smart phone that had been retired and has no service. I mount it to the handlebar using a cheap handlebar mount. It will overwrite files and your space is limited only by the size of your sd card. I can get maybe 4 hours of use out of it before my cell phone battery dies, but I could plug in an external charger to extend that significantly. I just have to remember to start the app and make sure it's mounted with the camera facing forward and it's good to go. I like it better than the Contour as it's much more flexible as you can use any smartphone you have lying around. I have 7 old smartphones so I could install a front, a back, and 2 sideways dashcams and it wouldn't cost me a dime, Also, your recording quality is limited only by the quality of the smartphone camera. The current phone I am using has just a 5MP camera but the recording quality seems just fine. It has some nice features like showing stats like speed and altitude on the playback. Dailyroads Vogager is just 1 of many free dashcam apps I saw on the Play Store. i seem to remember checking out a few others but found all but Dailyroads Voyager deficient in some way.