user23325: My Arduino Nano Every runs at 16Mhz (but the 4809 can support internal 20Mhz).
I know it may be possible to alter the boards.txt file and set it to build for 20Mhz.
However, I can't find the boards.txt for these new boards (MegaAVR).
Where is the boards.txt located?

user81152: In addition to set the
nona4809.build.f_cpu=20000000L

you will have to set the corresponding fuse byte to
nona4809.bootloader.OSCCFG=0x02

this enables the 20 MHz clock.

23325: <p>My Arduino Nano Every runs at 16Mhz (but the 4809 can support internal 20Mhz).<br />
I know it may be possible to alter the boards.txt file and set it to build for 20Mhz.
However, I can't find the boards.txt for these new boards (MegaAVR).
Where is the boards.txt located?</p>
 81152: <p>In addition to set the</p>
<pre><code>nona4809.build.f_cpu=20000000L
</code></pre>
<p>you will have to set the corresponding fuse byte to</p>
<pre><code>nona4809.bootloader.OSCCFG=0x02
</code></pre>
<p>this enables the 20 MHz clock.</p>
