Testing network speed on macOS:

networkQuality

Example output:

Downlink: capacity 24.052 Mbps, responsiveness 321 RPM - Uplink: capacity 0.000
Downlink: capacity 24.052 Mbps, responsiveness 294 RPM - Uplink: capacity 20.669
Downlink: capacity 24.548 Mbps, responsiveness 250 RPM - Uplink: capacity 20.669
Downlink: capacity 24.548 Mbps, responsiveness 248 RPM - Uplink: capacity 17.763
Downlink: capacity 26.099 Mbps, responsiveness 243 RPM - Uplink: capacity 17.763
Downlink: capacity 26.099 Mbps, responsiveness 243 RPM - Uplink: capacity 16.716
Downlink: capacity 26.567 Mbps, responsiveness 240 RPM - Uplink: capacity 16.716
Downlink: capacity 26.567 Mbps, responsiveness 240 RPM - Uplink: capacity 16.632
Downlink: capacity 27.436 Mbps, responsiveness 237 RPM - Uplink: capacity 16.632
Downlink: capacity 27.436 Mbps, responsiveness 235 RPM - Uplink: capacity 15.908
Downlink: capacity 27.120 Mbps, responsiveness 194 RPM - Uplink: capacity 15.908
Downlink: capacity 27.120 Mbps, responsiveness 185 RPM - Uplink: capacity 16.711
Downlink: capacity 25.164 Mbps, responsiveness 156 RPM - Uplink: capacity 16.711
Downlink: capacity 25.164 Mbps, responsiveness 150 RPM - Uplink: capacity 16.939
Downlink: capacity 24.892 Mbps, responsiveness 124 RPM - Uplink: capacity 16.939
Downlink: capacity 24.892 Mbps, responsiveness 118 RPM - Uplink: capacity 17.627
Downlink: capacity 23.011 Mbps, responsiveness 108 RPM - Uplink: capacity 17.627
Downlink: capacity 23.011 Mbps, responsiveness 100 RPM - Uplink: capacity 15.339
Downlink: capacity 22.093 Mbps, responsiveness 87 RPM - Uplink: capacity 15.339
Downlink: capacity 22.093 Mbps, responsiveness 85 RPM - Uplink: capacity 13.592
Downlink: capacity 23.291 Mbps, responsiveness 63 RPM - Uplink: capacity 13.592
Downlink: capacity 23.291 Mbps, responsiveness 63 RPM - Uplink: capacity 14.177
Downlink: capacity 23.291 Mbps, responsiveness 43 RPM - Uplink: capacity 17.627 
==== SUMMARY ====
Uplink capacity: 17.627 Mbps
Downlink capacity: 23.291 Mbps
Responsiveness: Low (43 RPM)
Idle Latency: 19.708 milliseconds

Step before: Trying to connect to a server with a SSH key. System: OSX, Big Sur

Connecting to a Server via SSH fails:

georg@Fischer ~ % ssh trembl@myserver -v           
OpenSSH_8.1p1, LibreSSL 2.7.3
debug1: Reading configuration data /Users/georg/.ssh/config
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 47: Applying options for *
debug1: Connecting to myserver.com port 22.
ssh: connect to host myserver.com port 22: Operation timed out

Did not work for ca. 1 hour. Same connection problem to different account with same provider, other account with same provider worked.

(Possible) Solution: Intentionally mis-spelled username, -v not stopping and timing out, log-in now possible.

Update 1

Use

nmap -Pn -p22 myserver

to check if the port is open or filtered.

Host discovery disabled (-Pn). All addresses will be marked 'up' and scan times will be slower.
Starting Nmap 7.91 ( https://nmap.org ) at 2021-03-30 14:15 JST
Nmap scan report for trembl@myserver (xx.xx.xxx.xxx)
Host is up (0.21s latency).
rDNS record for xx.xx.xxx.xxx: xx.xx.xxx.xxx

PORT   STATE     SERVICE
22/tcp filtered  ssh

It should say:

PORT   STATE SERVICE
22/tcp open  ssh

Update 2

Creating a ssh connection to the server from another computer (on the same network) worked. Somehow, after that check, the connection on this computer also worked. Very mysterious.

Update 3

Approach 2 did not work the next time. Switching to a different network (phone hotspot) worked. Maybe restarting the router?

Doing a Search and Replace on the shell should not be difficult:

find . -name "*.html" -exec sed -i "s/searchPattern/replacePattern/g" {} +

However, on macOS this error message occurs:

sed: 1: "./aaa/a ...": invalid command code .
sed: 1: "./aaa/b ...": invalid command code .
sed: 1: "./aaa/c ...": invalid command code .
...

It turns out, on MacOS the -i parameter needs to be followed by an empty string:

find . -name "*.html" -exec sed -i "" "s/searchPattern/replacePattern/g" {} +