It seems the Mylyn dependency is not statisfied.
Error details:
Cannot complete the install because of a conflicting dependency.
Software being installed: SonarLint for Eclipse 5.2.0.18685 (org.sonarlint.eclipse.feature.feature.group 5.2.0.18685)
Software currently installed: Mylyn Task List 3.25.1.v20200514-1748 (org.eclipse.mylyn_feature.feature.group 3.25.1.v20200514-1748)
Only one of the following can be installed at once:
Mylyn Commons 3.24.2.v20180904-2231 (org.eclipse.mylyn.commons.core 3.24.2.v20180904-2231)
Mylyn Commons 3.25.1.v20200511-1958 (org.eclipse.mylyn.commons.core 3.25.1.v20200511-1958)
org.eclipse.mylyn.commons.core 3.25.0.v20190131-2250
Cannot satisfy dependency:
From: Mylyn Commons 3.25.1.v20200511-1958 (org.eclipse.mylyn.commons.feature.group 3.25.1.v20200511-1958)
To: org.eclipse.equinox.p2.iu; org.eclipse.mylyn.commons.core [3.25.1.v20200511-1958,3.25.1.v20200511-1958]
Cannot satisfy dependency:
From: Mylyn Task List 3.25.1.v20200514-1748 (org.eclipse.mylyn_feature.feature.group 3.25.1.v20200514-1748)
To: org.eclipse.equinox.p2.iu; org.eclipse.mylyn.commons.feature.group [3.25.1,4.0.0)
Cannot satisfy dependency:
From: SonarLint for Eclipse 5.2.0.18685 (org.sonarlint.eclipse.feature.feature.group 5.2.0.18685)
To: org.eclipse.equinox.p2.iu; org.eclipse.mylyn.commons.core [3.24.2.v20180904-2231,3.24.2.v20180904-2231]