I came across a post from an Ethiopian Orthodox Christian in an Orthodox forum. The poster says that they observe (among many Jewish traditions) the sabbath & the Sunday worship ( see #9 in the list):
Matt 5:17 - “I did not come to abolish the Law”
1. We have Ark Processions year-round
2. We abstain from all unclean food (Halal, pork, shrimp, crab, etc)
3. We do no enter church if we are unclean (men and women)
4. We wear all white shawls (Netelas) as a symbol of Christ’s Resurrection and spiritual purity
5. We have a shoeless entry (not just during communion)
6. We abstain from any modern instruments (piano, guitar, etc)
7. We have 81 books in the Bible
8. We go of Halachic Jewish Time (Fasting entry and exits are based of our sun and star movements (Twilight) and our hours are reversed (12=6, 9=3)
9. We observe Friday evening and Saturday as the Sabbath (in addition to Sunday)
10. Women after giving birth have to wait 40 days or 80 days to enter church. ( Lev 12)
The EOTC is the only orthodox nation who incorporates 4000 year old Jewish customs (Judeo-Christianity) and Jewish forms of worship and tradition into its faith.
While other orthodox nations (Egypt, Armenia, Syrian, Indian, Greece, Russia, etc) were worshiping pagens and practicing cults , Ethiopia was the only to- be orthodox nation that was strictly observing Judaism and worshiping the God of Israel. 2000 years of Judaism and 2000 years of Christianity is the history of Ethiopia. We were the only ones that came into Christianity from its former faith, hence why we have stricter laws and ways of worship.