Thanks, it turns out I did have a copy of the elgg .htaccess in my elgg directory.  It has         

Options Indexes FollowSymLinks MultiViews

but none of the other ones:

        AllowOverride All
        Order allow,deny
        allow from all
        Require all granted

I'm now also getting net::ERR_ABORTED 508 (Loop Detected)  on some .mjs files.

I wonder if it's a race condition, since the ISP is much slower than my local server.  I can try to throttle my local server to see if similar problems show up.

If all else fails, I'll install another instance of elgg again in a different subdirectory.

I'll see if my ISP can come up with some insights, and will update here in case it helps anyone else! 

Looks like the problem was with the ISP, maxed out on number of "entry processes" (the number of processes the web server can spawn). 

But also seems something else was causing this to happen.  They fixed it, but haven't told me what they changed.  I will ask again, and if I find out, I will update here.

Just going to the "create group" page on elgg caused over 10 entry processes.  Sounds like something is misconfigured!

ISP or hosting provider?

Advanced way is to override this file in your custom plugin.

(You can start with this skeleton plugin.)

Create a new folder 'assets' in your data directory.

Put your logo to this folder, e.g.:

assets/topbar_logo.png

Copy the mentioned file to your custom plugin and change code on:

$asset_src = elgg_get_simplecache_url('assets/topbar_logo.png');


$logo = elgg_format_element('img', [
    'src' => $asset_src,
    'alt' => elgg_get_site_entity()->getDisplayName(),
]);


echo elgg_format_element('div', [
    'class' => 'elgg-heading-site'
], elgg_view('output/url', [
    'text' => $logo,
    'href' => elgg_get_site_entity()->getURL(),
    'title' => elgg_get_site_entity()->getDisplayName(),
]));

Thanks Nikolai,

It's very hard, but i will try