70D won't turn on

[1stSolo]

This 70D is 9 years old and had been my workhorse all this time. I'm doing daytime nature and astrophotography, timelapses of Milky Way and deep sky photos.
A few days ago decided to record a music video with it. It was on AC/DC power adapter because battieries drain fast when display is always on and an extra light is connected to the accessory shoe.
Noticed the camera and the microSD card had become very hot, and "Err" is displayed on LCD display. No code, just "Err". Turned it off, let it cool, then turned on again. It was showing a frozen frame on the monitor and "Err" on LCD. Cycpled power again and it never turned on again, neither on AC/DC nor Canon battery power.
Talked to a couple of local camera repair shops. One quoted $178 to replace DC-DC converter, the other said I have a dead brick because "70D has a design flaw where heat sink on CPU is inadequate for dissipating heat and shooting video for a long time can fry the CPU. Replacing a motherboard costs more than a used 70D on the market and I'm better off throwing this out and paying $1000 for 80D or 90D".
Also contacted Canon repair and automated system quoted $0.00 to send it in for repair.
I scanned through Canon Community Forums and it seems like a relatively common problem.
So if I send it to Canon, are they going to slap me with the bill later or they are treating it as a recall and replacing burned motherboards?
I was considering switching to Sony for a while, but I've been a Canon guy since 1980s when 36mm EOS-1 came out (still have one in working condition along with 20D) and all my lenses, accessories and printers are Canon. Am I having attachment issues? Help me save my friend!

[ebiggs1]

My first thoughts is the 70D as a platform would not be my first choice for long video work. Certainly draining two batteries I would consider a long time. The 70D is just about in the transition time area. It shoots video but it really isn't a video camera.

I know the latest crop of cameras seem to have no or at least few issues shooting video. I imagine Canon realized the need and designed them differently. I hate to say better but that's really what they did. If your goal is mostly video you might want to upgrade now anyway. I am not sure even the 90D would be a whole lot better (doing mostly video) but it probably is better.

One of the new mirrorless cameras would be my choice. The 90D is a grandtastic stills DSLR. It is the best crop style DSLR made, IMHO. I have always though, after spending a day with one, I would buy a 90D with the again grandtastic Sigma 18-35mm f/1.8 DC HSM Art Lens. Say what you want about FF but that combo is as good as it gets.