What is the easiest way to connect multiple ground wires?

[frosty thorn]

Without using a breadboard or custom PCBs

[sage ridge]

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[little schooner]

Something like: https://www.gordonelectricsupply.com/p/Nsi-Wc-R-Sj-Standard-Red-Easy-Twist-22-10-Awg-Small-Jar-Of-100/5981387?utm_source=bing&utm_medium=cpc&utm_campaign=NSI&msclkid=434ae92ba2e61dc1d1cf8d9cf6ee5023

Read how to REALLY use them, but they are satisfactory for home wiring uses in code.

[wicked kiln]

https://www.amazon.com/Wago-221-413-LEVER-NUTS-Conductor-Connectors/dp/B077WZV3D4/ref=sr_1_4?crid=JJT8JSJP5NVL&keywords=levernuts&qid=1689742227&sprefix=levernuts%2Caps%2C90&sr=8-4

or just twist+solder