I have been using dual monitors (HP and Dell) with no issues on my MacBook Pro running 10.14.5 for 6 months. Dell is connected to HDMI and HP is connected to Thunderbolt. After a few recent OS updates I found that my Dell monitor will frequently drop into a flicker or flashing mode where screen blacks out for a fraction of a second every 2-5 seconds. Have tried all recommended solutions with no luck in finding a permanent fix. Curious if anyone has found a fix?
I did find that a power cycle on the Dell monitor (physically disconnect/reconnect power cord) will stop the flicker temporarily but the flicker typically returns 2-8 hours later.